The third command in the solid editing group is called Thicken. This command is used to add thickness to a generally curved surface. To start the Thicken command, you can type the command name, THICKEN (or just type TH), and then press Enter. Alternatively, you can click on the Thicken button found in the Create panel in the 3D Basics workspace, as shown in the following screenshot:

If you are using the 3D Modeling workspace, you will find the Thicken button in the Solid Editing panel on the Home tab, or in the Boolean panel on the Solid tab.

The Thicken command is used to create 3D solid objects by adding thickness to a surface. It can be used as follows:

1. Start the Thicken command.
2. Select the surface(s) to be thickened and then press Enter to end the selection stage.
3. Type the required thickness value using the keyboard and then press Enter.
4. The surface will be thickened and the command terminates.

The following diagram is an illustration of the previous steps:

If you select the thickened object, you will find a number of grab points. All of these points act like base points, from which you can grab and move the object, as shown here. They cannot be used to modify the thickened object, as shown in the following diagram:

As demonstrated in the previous example, the Thicken command is very similar to the extrude command. One difference between these two commands is the fact that the latter cannot be used with curved surfaces, the surface must be planar for the extrude command to work, while the Thicken command can generally work with any surface, as shown in the previous example. Another difference is the fact that the extrude command works with surfaces, regions, and polylines, and if the polyline is closed, it will automatically generate a 3D solid object, while the Thicken command is limited to surface objects. This command won't work with regions or closed polylines. The following table summarizes the differences between the extrude and Thicken commands, and for more details on the extrude command, please refer to Chapter 12, Conversion between 2D and 3D:

By default, the original surfaces used will be deleted once the Thicken command terminates. You can control whether to delete these objects by using the DELOBJ system variable. To access this, just type DELOBJ and then press Enter. The current value of the DELOBJ system variable will be displayed, and then you can type the new value and press Enter. For more details regarding the DELOBJ system variable, please refer to Chapter 12, Conversion between 2D and 3D.

Now that we have learned how to use the different solid editing tools in AutoCAD, let's take a look at the next group of modify commands that are specific to face editing